This invention relates generally to inflators for use in inflating inflatable restraint airbag cushions, such as used to provide impact protection to occupants of motor vehicles. More particularly, the invention relates to plural stage inflators such as may provide an inflation gas output which is adaptive to factors such as one or more crash and occupant conditions.
It is well known to protect a vehicle occupant using a cushion or bag, e.g., an "airbag," that is inflated or expanded with gas when the vehicle encounters sudden deceleration, such as in a collision. In such systems, the airbag cushion is normally housed in an uninflated and folded condition to minimize space requirements. Upon actuation of the system, the cushion begins being inflated in a matter of no more than a few milliseconds with gas produced or supplied by a device commonly referred to as "an inflator."
Various types of inflator devices have been disclosed in the art for the inflation of an airbag such as used in inflatable restraint systems. One type of known inflator device derives inflation gas from a combustible pyrotechnic gas generating material which, upon ignition, generates a quantity of gas sufficient to inflate the airbag.
A second type of known inflator device forms airbag inflation gas from a combination of stored compressed gas and the combustion of a solid form of a pyrotechnic gas generating material. This type of inflator device is commonly referred to as a hybrid inflator.
A new type an inflator, called a "fluid fueled inflator," has been developed. Such inflators are the subject of commonly assigned Smith et al., U.S. Pat. No. 5,470,104, issued Nov. 28, 1995; Rink, U.S. Pat. No. 5,494,312, issued Feb. 27, 1996; and Rink et al., U.S. Pat. No. 5,531,473, issued Jul. 2, 1996, the disclosures of which are fully incorporated herein by reference.
Such inflator devices utilize a fuel material in the form of a fluid, e.g., in the form of a gas, liquid, finely divided solid, or one or more combinations thereof, in the formation of an inflation gas for an airbag. In one such inflator device, the fluid fuel material is burned to produce gas which contacts a quantity of stored pressurized gas to produce inflation gas for use in inflating a respective inflatable device.
In view of possibly varying operating conditions and, in turn, possibly varying desired performance characteristics, there is a need and a desire to provide what has been termed an "adaptive" inflator device and corresponding inflatable restraint system. With an adaptive inflator device, output parameters such as the quantity, supply, and rate of supply of inflation gas, for example, can be selectively and appropriately varied dependent on selected operating conditions such as ambient temperature, occupant presence, seat belt usage and rate of deceleration of the motor vehicle, for example.
While such adaptive systems are desirable, they typically require the inclusion of additional components as a part of the associated inflator device, thus increasing the size of the inflator. As such it has been even more difficult to provide an adaptive inflator which will meet the size requirements for vehicles, especially for driver side applications.
Thus, there remains a need for an adaptive inflator device of simple design and construction will meet the size requirements for vehicles, especially for driver side applications.